The effects of dopamine applied by microiontophoresis to nerve cells in the subthalamic nucleus were studied in rat brain. It has been shown by other investigators that the systemic administration of the dopamine agonists, amphetamine and apomorphine, increases glucose utilization in this structure. The purpose of this project was to study the electrophysiologic characteristics of the dopamine response, in terms of the neuronal firing rate, determined by extracellular recording techniques. The responses of these neurons to dopamine has been found to be heterogeneous, with both increases and decreases in firing rate observed in different neurons.